Many polymers, particularly synthetic elastomers, are produced for commercial consumption in a particle- or particulate-form such as pellets, granules, briquettes, pills, crumb, flakes, spheres, disks, cylinders, cubes, and various other regular and irregular shapes. Generally, the shape of these polymer particles is either deliberately formed or a natural result of various recovery and drying operations in the polymer production process. The particulate-form of the polymers may be desirable for many applications because such polymer particles can be compounded with other polymers more readily than large polymer blocks, sheets, or the like. Further, the polymer particles can be handled easier for further uses and/or dissolved more readily in oils to make lubricating oils and the like.
However, the convenient-to-use particles of many polymers, particularly those exhibiting any elastomeric character, generally tend to agglomerate together or exhibit “blocking”, which is an undesirable adhesion among contacting particles. Such agglomeration often occurs under elevated temperature and/or pressure during the storage of the polymer particles. For example, the pressure caused by stacking bales or packages of the polymer particles may create conditions favorable for agglomeration. If the polymer particles agglomerate, then generally it is necessary to grind, crush, or otherwise masticate the agglomerates to re-separate the polymer particles partially or completely to produce a utilizable particulate material. Such mechanical processes can be burdensome and undesirable because of additional labor, time and cost, inconvenience of using them, and the potential risks of contamination and/or degradation of the polymer during the additional processes.
There are some attempts of preventing the blocking of polymer particles which include applying a dusting agent such as carbon black, talc, zinc stearate, rice flour, chalk, magnesium oxide, infusorial earth, or the like, to the polymer particles in an effort to counteract the natural tackiness or blockiness of the polymer particles. However, adding the dusting agent to the polymer may be undesirable for some applications because the dusting agent itself may be undesirable for the applications, such as lubricating oils for modern engines, the performance of which may be affected by the undesirable dusting agent. Further, silica powder and some fine grades of talc may possibly pose health hazards under some circumstances.
In some instances, some polymer articles may also stick together as the above-mentioned polymer particles. For example, films of polyolefin resins, such as polyethylene and polypropylene, are available for applications as wrapping films for food, fibers, pharmaceutical preparations, fertilizers, and other notions or as agricultural covering materials. To improve film handling in some processes of making or using the films, an inorganic anti-blocking agent, such as silica, talc and zeolite, may be added to the polyolefin films. However, the addition of a large quantity of inorganic anti-blocking agent may deteriorate the transparency and appearance of the polyolefin films and may lower their resistance to surface scratches.
Therefore, there is a need for an improved method to reduce the adhesion or stickiness among polymer particles. Further, it is desirable that the method can achieve a well-balanced improvement in some desirable properties such as anti-blocking properties, transparency, and sliding properties.